The present invention relates to an electrophotographic image forming apparatus and an exposure method therefor.
Apparatuses conventionally known as electrophotographic image forming apparatuses include those executing image stabilization control composed of forming a plurality of specified toner patterns with varied intensities of laser emission from a laser diode (LD) serving as an exposure light source of an exposure device, detecting the density of each toner pattern by a sensor, attaining the relation between the laser emission intensity and the toner density based on attained detection results, and determining an optimum intensity of light emission which makes it possible to provide an optimum density based on the attained relation, and executing image formation with the determined optimum intensity of light emission in the subsequent printing operation (see JP 2004-21139A).
In recent years, image forming apparatuses having two exposure light sources in an exposure device for forming electrostatic latent images on photoreceptors by simultaneously emitting light from the respective exposure light sources in order to increase a printing speed have been put to practical use. In this type of image forming apparatuses, if dots formed on the photoreceptor by the respective exposure light sources have variations between the respective exposure light sources, then image noise is generated particularly in the case of forming halftone images.